As mobile communications and satellite navigations advance, a navigation apparatus such as a global positioning system (GPS) device, a mobile phone with a navigation function or a digital personal assistant with a navigation function becomes indispensable to of our daily life. During being transmitted from a satellite to the ground, the satellite positioning signal is easily affected due to factors and interferences such as various types of terrains, shelters, satellite time errors or signal delays, so the position data calculated by the global positioning system (GPS) often have errors, and thus an apparatus or a method is required to generate an offset for correcting the position data in order to provide a precise positioning on a navigation map.
In a prior art, a method of correcting the position data has been disclosed, and such method builds at least one differential global positioning system (DGPS) base station with a known reference position in advance. After receiving the satellite signals and calculating a position data according to the received satellite signals, the DGPS base station can obtain an offset by comparing the position data with latitude and longitude coordinates of the known reference position, and then transmit the offset to a navigation apparatus by a transmission module. The navigation apparatus includes a built-in differential global positioning system (DGPS) receiver for receiving the offset which can be used to correct the position data generated from the global positioning system (GPS), so that the precision of the map matching of the navigation apparatus can be improved.
However, the aforementioned prior art has the drawbacks of building at least one differential global positioning system (DGPS) base station, and the navigation apparatus also requires an additional differential global positioning system (DGPS) receiver. In other words, this method requires additional costs for hardware and software. Furthermore, if the navigation apparatus is at a location where no differential global positioning system (DGPS) base station is reachable or the navigation apparatus does not come with a differential global positioning system (DGPS) receiver, such method in prior art becomes useless.
To overcome the drawbacks of the prior art, and satisfy user requirements of the navigation apparatus, the inventor of the present invention according to years of experience in the related field to conduct extensive researches and experiments, and finally developed a navigation apparatus capable of correcting position data according to map matching position and its method in accordance with the present invention.